In recent years, the introduction of an architecture called a Centralized Radio Access Network (C-RAN) is being studied in a wireless communication system in compliance with a cellular scheme.
In the C-RAN, a baseband unit (BBU) that performs processing on a baseband signal and a remote radio head (RRH) that performs conversion between a baseband signal and a radio frequency (HF) signal and transmission and reception of the radio frequency (RF) signal are physically separated from each other. The C-RAN employs a configuration such that one BBU positioned in a centralized control station and a plurality of RRHs arranged in a distributed manner are connected with an optical fiber cable or the like.
With this C-RAN configuration, an improvement in communication quality is possible by arranging the plurality of RRHs in a distributed manner so as to be at a short distance from a terminal. Because of this, extension of flexible coverage is possible. Furthermore, because one BBU can control the plurality of RRHs, cooperative operations among the plurality of RRHs can be performed easily. In the plurality of RRHs that make connections to the same BBU, a problem of interference can be controlled by performing the cooperative operation.
However, there is a limit on the number of RRHs that can make connections to one BBU. Furthermore, there is a problem that, because the cooperative operation is difficult between each of the RRHs that make connections to different BBUs, interference occurs due to a signal that is transmitted from an RRH different from the one the terminal is communicating with.
In order to address this problem, for example, NPL 1 discloses a technology in which the problem of the interference between each of the RRHs that make connections to different BBUs is solved by transmitting and receiving information for transmission control of the RRH between each of the BBUs.